1. Field of the Invention
The present invention relates to a junction unit to be assembled later into an internal sheet discharge space to convey a sheet toward a post-processing unit and an image forming apparatus provided with such a junction unit.
2. Description of the Background Art
An image forming apparatus of a so-called internal discharge type including a space, into which a sheet after image formation is to be discharged, in an apparatus main body has advantages of smaller space occupancy and good storage property since a sheet tray or the like does not project from the apparatus main body. On the other hand, a post-processing unit for applying post processings such as punching and stapling may be optionally attached later to such an image forming apparatus of the internal discharge type. Generally, a discharge opening for sheets is facing an internal discharge space, and the internal discharge space is small and it is difficult to install the post-processing unit in this space.
In a conventional apparatus, in the case of attaching a post-processing unit later, the post-processing unit is installed on a side wall portion of an apparatus main body (side wall opposite to the one where a sheet discharge opening is provided) and a junction unit including a sheet conveying function is assembled in the internal discharge space. A sheet is conveyed from the discharge opening to the post-processing unit via this junction unit. Note that the junction unit is fixed to the apparatus main body by screws or the like, and a user cannot easily detach the once assembled junction unit from the internal discharge space.
Also in the junction unit, a sheet jam may occur similar to other sheet conveyance paths. As an anti-jam measure, it is necessary to make a sheet conveyance path of the junction unit openable. In a conventional apparatus, a cover having an upper guide surface is rotatably mounted on a base having a lower guide surface. A rotary shaft is provided at the back side of the cover, and the rotary shaft is rotatably supported on a vertical wall standing on the base at the back side.
However, the construction of the conventional apparatus has a disadvantage that the size of the junction unit including a rotation supporting portion is large. Except when the internal discharge space is relatively large, the construction of the conventional apparatus is unsuitable for a small image forming apparatus having a relatively small internal discharge space, and a junction unit which can be miniaturized is required.